ATV

Small but perfectly powerful

18 January 2012

Satellite propulsion systems contain a great deal of top-class technology

Specialising in this field, the Lampoldshausen site has become a centre of excellence unique to its kind anywhere in Europe. These days, any European satellite not equipped with engines from Lampoldshausen is likely to be a rarity.

Compared to the Vulcain engine on the Ariane, satellite engines seem really tiny. Yet they fulfil exactly the same task – they generate thrust. The purpose of the miniature engines, however, is not to unleash gigantic thrust forces, but to provide carefully measured pulses that will help satellites and probes to reach and maintain their final trajectory and orbit position. Utmost precision and reliability is the order of the day, and it has to last throughout the 15-year service life of the satellite. Four different types of engine are built for satellite propulsion systems, and they are constantly being improved.

Single-component 1N engine

The 1-Newton engine is about the size of a small electric torch and weighs only 300 gram. The engine is suitable both for continuous operation and for large numbers of short pulses. It uses hydrazine as its fuel. The hydrazine is ignited in a catalytic converter and transforms energy into thrust. The 1-Newton engine has long been successfully used for the orbit and attitude control of smaller models, such as scientific or Earth observation satellites.Two-component 10N + 22N engines

The thrust for these engines is generated when a fuel and an oxidizer are brought together. The tanks for each substance have a capacity of approximately 1,400 litres. The oxidizer is a mixture of nitrogen and oxygen, while the fuel is usually hydrazine. There is no need for a catalytic converter. Combustion, and therefore thrust, takes place as soon as the two substances are injected into the combustion chamber and form a compound. The resulting reaction is what causes combustion. 10N and 22N engines are used for larger satellites, such as telecommunications satellites. The 10-Newton engine has an output of about 20 hp and is one of Airbus Defence and Space’s most successful products. More than 80 satellites are flying, or have flown, with these engines, including the communications satellites of all major operators. The 22-Newton engine is the latest product in the family of two-component engines. Just like the 10-Newton engine, this propulsion system is suitable for the orbit and attitude control of larger satellites.

From single-seat to double-seat

The specialists at Airbus Defence and Space are constantly developing new technologies or updating existing ones. Over the years, for instance, even the successful 10N engine has undergone a complete overhaul. It originally had a single valve through which the fuel was injected into the combustion chamber. The new double-seat engine is fitted with two valves. The previously used single-seat engines were not able to switch to a second valve in the event of a failure. If the worst came to the worst, a whole engine group had to be shut down. All new-generation 10N engines are equipped with double-seat technology.

400N apogee engine

This two-component engine outclasses any car engine: It produces 850 hp but only weighs 3.5 kg. It serves as an apogee engine, enabling geostationary satellites to reach their final orbit at an altitude of 36,000 kilometres after being released by the launch vehicle, or as propulsion for research probes that fly far out into space. Over 60 satellites and probes have already been equipped with this power pack. Like the 10-Newton engine, it is used in numerous communications satellites operated by the world’s leading companies.

How does the fuel get into the combustion chamber?

All the engines on a satellite are arranged such that they do not adversely affect any technical equipment such as radar facilities or antennas with the exhaust fumes that they continually produce. This means the fuel and the oxidizer may have to cover rather a long distance from the tank to the engine. In order to generate sufficient pressure, the propulsion system has two high-pressure tanks filled with the propellant gas helium. The helium is introduced into the system via pyrovalves, filters, controllers and pressure-measuring transducers, and generates pressure in a similar way to a bottle of hair-spray. The helium ensures that there is sufficient feed pressure in the fuel tanks and thus that the fuels are evenly injected into the engines. These helium tanks hold 50–90 litres.

Unified Propulsion System (UPS)

To maximise the satellites’ service life while saving as much weight as possible, Airbus Defence and Space’s Lampoldshausen plant developed the UPS (Unified Propulsion System). The UPS is made up of four components: the apogee engine, up to 16 miniature engines, high-pressure tanks and fuel tanks. Airbus Defence and Space is the only space company in the world to offer a complete system of this kind successfully on the commercial market. The decision to provide complete propulsion systems enabled Lampoldshausen to expand its position considerably, especially on the European telecommunications market, where Airbus Defence and Space meanwhile holds a market share of approximately 90%. Both major European satellite platforms, Eurostar and Spacebus, are equipped with propulsion systems from Lampoldshausen. Six to eight systems are delivered every year, with a total of 62 having been completed so far. The decision to deliver complete systems ready for integration was a simple question of manufacturing efficiency. Originally, the propulsion system used to be integrated into the satellites on site in Lampoldshausen. The result of this practice was that different types of work could never be carried out at the same time. Since the introduction of the UPS, it has become standard practice to ship complete systems to the integration centres in Cannes, Toulouse or Friedrichshafen. This has enabled the satellite lead time to be shortened considerably. The UPS is a Franco–German collaboration. The helium tanks, for instance, are manufactured at the Airbus Defence and Space site in Bordeaux, the fuel tanks in Bremen and the rest in Lampoldshausen.

The customer comes first

However, Airbus Defence and Space not only manufactures propulsion systems and equipment for deployment in space – the company also provides all the associated services through to a successful launch. Customers are given local support for satellite launches at the launch site, including Kourou in French Guiana, Cape Canaveral in the USA, Plesetsk in Russia and Baikonur in Kazakhstan. Experts from Airbus Defence and Space help to install the satellite in the launch vehicle, fuel the satellite and carry out the final tests of the satellite propulsion system before clearance is given for launch. Fuels are processed for use in spacecraft at Airbus Defence and Space’s own facilities and delivered to each launch site. Specially trained fuelling teams, along with fuelling and checkout facilities, are provided for the respective launch site.